U.S. patent number 6,672,409 [Application Number 09/695,156] was granted by the patent office on 2004-01-06 for downhole generator for horizontal directional drilling.
This patent grant is currently assigned to The Charles Machine Works, Inc.. Invention is credited to Matthew L. Dock, Brent G. Stephenson.
United States Patent |
6,672,409 |
Dock , et al. |
January 6, 2004 |
**Please see images for:
( Certificate of Correction ) ** |
Downhole generator for horizontal directional drilling
Abstract
A generator assembly for generating power in the downhole end of
a drill string used to form a borehole in horizontal directional
drilling. The drill string provides a fluid passageway in which the
downhole generator is receivingly disposed, at least in part, to
subject a rotatable turbine to a pressurized fluid flowing in the
fluid passageway, thereby imparting a mechanical rotation to the
turbine. The turbine is coupled to a generator so that the
mechanical rotation of the turbine is transferred to a power output
of the generator.
Inventors: |
Dock; Matthew L. (Stillwater,
OK), Stephenson; Brent G. (Stillwater, OK) |
Assignee: |
The Charles Machine Works, Inc.
(Perry, OK)
|
Family
ID: |
24791839 |
Appl.
No.: |
09/695,156 |
Filed: |
October 24, 2000 |
Current U.S.
Class: |
175/107;
166/66.5; 175/101; 175/62 |
Current CPC
Class: |
E21B
7/046 (20130101); E21B 41/0085 (20130101) |
Current International
Class: |
E21B
7/04 (20060101); E21B 41/00 (20060101); E21B
004/02 (); E21B 007/01 () |
Field of
Search: |
;166/66.5
;175/62,93,92,100,101,107 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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197 06 371 |
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Aug 1998 |
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DE |
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199 55 345 |
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Jun 2001 |
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DE |
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0 520 733 |
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Dec 1992 |
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EP |
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0 747 568 |
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Dec 1996 |
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EP |
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2 346 509 |
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Aug 2000 |
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GB |
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WO 01/51761 |
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Jul 2001 |
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WO |
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Primary Examiner: Bagnell; David
Assistant Examiner: Gay; Jennifer H
Attorney, Agent or Firm: McKinney & Stringer, P.C.
Claims
What is claimed is:
1. A horizontal directional drilling machine, comprising: a drill
string; a fluid flow passage to direct fluid along the drill
string; and a generator assembly to generate an output power, the
generator assembly comprising: a generator housing supportable by
the drill string, the generator housing defining a cavity; an inlet
and an outlet in the generator housing; a turbine assembly
supported in the cavity; an electric generator driven by the
turbine; and a bypass assembly to maintain a substantially constant
fluid flow rate through the inlet.
2. The horizontal directional drilling machine of claim 1
comprising a dipole magnetic field transmitter electrically
connected to the generator assembly.
3. The horizontal directional drilling machine of claim 1
comprising a ground penetrating radar apparatus electrically
connected to the generator assembly.
4. The horizontal directional drilling machine of claim 1
comprising an electrical control circuit electrically connected to
the generator assembly.
5. The horizontal directional drilling machine of claim 1 further
comprising a tool head joined to the drill string, wherein the
generator assembly is supported in the tool head.
6. The horizontal directional drilling machine of claim 1 wherein
the turbine assembly is magnetically coupled to the electric
generator.
7. The horizontal directional drilling machine of claim 6 wherein
the generator housing seals the electric generator from the fluid
flow passage.
8. The horizontal directional drilling machine of claim 6 wherein
the electric generator comprises a wound coil excitable by rotation
of the turbine assembly.
9. The horizontal directional drilling machine of claim 6 wherein
the electric generator is electrically connected to a battery.
10. The horizontal directional drilling machine of claim 6 wherein
the inlet and the turbine assembly are positioned to cause fluid to
impinge the turbine assembly substantially orthogonal to the axis
of rotation of the turbine assembly.
11. The horizontal directional drilling machine of claim 10 wherein
the turbine assembly comprises a plurality of radially extending
vanes.
12. The horizontal directional drilling machine of claim 1 wherein
the inlet and the turbine assembly are positioned to cause fluid to
impinge the turbine assembly substantially orthogonal to the axis
of rotation of the turbine assembly.
13. The horizontal directional drilling machine of claim 12 wherein
the turbine assembly comprises a plurality of radially extending
vanes.
14. The horizontal directional drilling machine of claim 1 wherein
the output power is electrical power.
15. A generator assembly for powering an electric component used
with a horizontal directional drilling system, the generator
assembly comprising: a generator housing supportable by the drill
string, the generator housing defining a cavity; an inlet and an
outlet in the generator housing; a fluid driven turbine assembly
supported in the cavity; an electric generator driven by the
turbine; and a bypass assembly to maintain a substantially constant
fluid flow rate through the inlet.
16. The generator assembly of claim 15 wherein the inlet and the
turbine assembly are positioned to cause fluid to impinge the
turbine assembly substantially orthogonal to the axis of rotation
of the turbine assembly.
17. The generator assembly of claim 16 wherein the turbine assembly
comprise a plurality of radially extending vanes.
18. The horizontal directional drilling machine of claim 15 wherein
the turbine assembly is magnetically coupled to the electric
generator.
19. The horizontal directional drilling machine of claim 18 wherein
the inlet and the turbine assembly are positioned to cause the
fluid to impinge the turbine assembly substantially orthogonal to
the axis of rotation of the turbine assembly.
20. The generator assembly of claim 19 wherein the turbine assembly
comprise a plurality of radially extending vanes.
21. The horizontal directional drilling machine of claim 15 wherein
the generator housing seals the electric generator.
22. A horizontal directional drilling machine comprising: a drill
string; a fluid flow passage to direct drilling fluid along the
drill string; a generator assembly supported in the drill string
and adapted to generate output power, the generator assembly
comprising a turbine assembly magnetically coupled to an electric
generator; a rechargeable battery electrically connected to the
generator assembly; and a dipole magnetic field transmitter
electrically connected to the rechargeable battery.
23. The horizontal directional drilling machine of claim 22 wherein
the generator assembly further comprises: a generator housing
defining a cavity; an inlet and an outlet in the generator housing;
and wherein the turbine assembly is supported in the generator
housing so that the inlet is positioned to cause the drilling fluid
to impinge the turbine assembly substantially orthogonal to the
axis of rotation of the turbine assembly.
24. The horizontal directional drilling machine of claim 22 wherein
the generator assembly further comprises: a generator housing
supported by the drill string, the generator housing defining a
cavity; an inlet and an outlet in the generator housing to direct
drilling fluid across the turbine assembly; and a bypass assembly
to maintain a substantially constant drilling fluid flow rate
through the inlet.
25. The horizontal directional drilling machine of claim 24 wherein
the turbine assembly is supported within the generator housing so
that that the inlet is positioned to cause the drilling fluid to
impinge the turbine assembly substantially orthogonal to the axis
of rotation of the turbine assembly.
Description
FIELD OF THE INVENTION
The present invention relates to the field of horizontal
directional drilling of boreholes, and in particular but not by way
of limitation, to an apparatus and an associated method for
generating power in the downhole end of a drill string used in near
surface horizontal directional drilling.
SUMMARY OF THE INVENTION
A horizontal directional drilling machine is provided that acts on
a drill string to form a borehole in the subterranean earth. The
drill string has a fluid flow passage for the pumping of a
pressurized fluid to the downhole end of the drill string to aid in
the formation of the borehole. A generator assembly is disposed, at
least in part, in the fluid flow passage and is responsive to the
fluid flowing in the fluid flow passage to generate power to meet
the downhole power requirements associated with horizontal
directional drilling.
In one embodiment of the present invention the generator assembly
has a housing supportable in the drill string so as to place a
cavity formed within the housing in the fluid flow passage. An
inlet in the housing directs the pressurized fluid into the cavity.
An outlet is furthermore provided in the housing permitting an
egress of fluid from the cavity.
An impeller is supported in the cavity for mechanical rotation in
response to an impinging engagement of the pressurized fluid
flowing from the inlet to the outlet. A generator is coupled to the
impeller to convert the mechanical rotation to a power output.
Other aspects and advantages of the present invention are apparent
from the description below and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic representation of a near surface
horizontal directional drilling machine acting on an uphole end of
a drill string which, in turn, supports a downhole generator that
is constructed in accordance with the present invention.
FIG. 2 is an exploded, partially broken away, isometric view of the
downhole portion of the drill string.
FIG. 3 is a diagrammatic partial cross sectional view of the tool
head of FIG. 2 with a generator assembly and a transmitter disposed
in the tool head.
FIG. 4 is a diagrammatic partial cross sectional view of the
generator assembly of FIG. 3.
FIG. 5 is a view taken along the line 5--5 of FIG. 4.
FIG. 6 is an enlarged view of a portion of the turbine wheel of
FIG. 5 at a position of the turbine wheel where the motive fluid is
operatively impinging one of the vanes of the turbine wheel.
FIG. 7 is a view similar to that of FIG. 6 wherein the turbine
wheel has rotated in a clockwise direction such that the motive
fluid is simultaneously operatively impinging two of the vanes of
the turbine wheel.
FIGS. 7A and 7B are elevational and top view, respectively, of an
alternative turbine wheel having an arcuate shaped contact
surface.
FIG. 8 is a diagrammatic partial cross sectional view similar to
FIG. 3 with the generator assembly disposed in an alternative
position within the tool head.
FIG. 9 is a diagrammatic partial cross sectional view of the
generator assembly of FIG. 8.
FIG. 10 is a diagrammatic partial cross sectional view of the
generator assembly constructed in accordance with an alternative
embodiment of the present invention.
BACKGROUND OF THE INVENTION
Near surface horizontal directional drilling is a widely-used
method of producing subterranean boreholes for the routing of
underground utilities. On a larger scale, horizontal directional
drilling can be used to place pipelines beneath above-ground
obstacles such as roadways or waterways. This is accomplished by
drilling an inclined entry borehole segment downward through the
earth surface, then drilling substantially horizontally under the
obstacle, then upwardly through the earth surface on the other side
of the obstacle as in accordance with, for example, U.S. Pat. No.
5,242,026, entitled METHOD AND APPARATUS FOR DRILLING A HORIZONTAL
CONTROLLED BOREHOLE IN THE EARTH; issued to Deken et al. and
assigned to the assignee of the present invention. Usually a pilot
bore is drilled in this manner and then a final reaming operation
is performed to produce the desired borehole. In any event, the
pipeline or other "product" being installed can then be pulled into
the borehole. Advantageously, all this is done without disturbing
the structure or the use of the obstacle. On a smaller scale,
electrical lines can be routed beneath fences and driveways in a
similar manner.
Conventionally, a horizontal directional drilling machine acts on a
drill string to produce the pilot hole. The drilling machine
imparts rotational and thrust forces to an upper end of the drill
string to rotate and advance a bit attached to the lower, or
downhole, end of the drill string. The downhole end of the drill
string is adapted to selectively guide the bit so as to steer the
downhole end of the drill string.
One way of steering the downhole end of the drill string is with a
slanted face bit. When the drill string is simultaneously rotated
and advanced, the offset bit forms a pilot hole in a substantially
straight direction. But when the drill string is advanced without
rotation, the bit pierces the subterranean earth and veers in a
different direction, as determined by the angle of the slanted face
and the rotational orientation of the drill string.
The bit is supported by a tool head attached to the downhole end of
the drill string. The tool head location can be tracked for
steering and direction-control to ensure that underground
obstacles, such as pipelines or electrical lines are avoided. One
common way of tracking involves positioning a transmitter in the
tool head that emits a signal, and detecting the signal with a
receiver that is positioned above ground. Typically, the receiver
is a portable device controlled by an operator above ground. Some
receivers detect not only the location but also orientation and
status information of the tool head. Information such as roll,
pitch, and azimuth, allows the drilling machine operator to
determine rotational orientation of the tool head in order to
selectively change direction of the bore when the drill string is
advanced without rotation. Other conditions are also monitored such
as tool head temperature, battery status, etc.
Advancements in horizontal directional drilling have been realized,
but unresolved difficulties remain. For example, tracking devices
are limited by power constraints of the transmitter. The demand for
more information from the transmitter has outpaced advancements in
the traditional way of powering the transmitter. Generally, the
transmitter emits a signal that is detectable within a
characteristic dipole magnetic field surrounding the transmitter.
In most cases, the transmitter uses a battery which provides a
relatively weak-powered signal. As a result, the effective
detection range of the dipole magnetic field generated by the
transmitter is limited by the weak signal. This can be problematic
at times, such as when drilling under roadways or waterways.
Clearly, more powerful transmitters are desirable in that they
permit deeper tracking as a result of their larger dipole magnetic
field. Furthermore, the finite life of a battery means that when
the battery is dissipated, the drill string must be withdrawn from
the borehole in order to replace it.
In other cases the transmitter is powered by a wire-line electrical
connection. Such a connection is difficult to maintain in the
relatively harsh environment associated with subterranean
directional drilling. The self-contained nature of a battery
powered transmitter is preferable in many cases, despite the
problem of limited power.
There is a long felt need in the industry for a self contained
electrical power generating assembly to provide a continuous power
supply adapted to meet the ever-increasing electrical power
requirements associated with horizontal directional drilling.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Beginning with FIG. 1 which is a diagrammatical representation of a
drilling machine 10 forming a borehole 14 into the subterranean
earth. The borehole 14 is selectively formed within a predetermined
zone of safe passage to avoid underground objects and above-ground
obstacles that would otherwise be disturbed by conventional
methods, such as trenching and backfilling.
It will be noted that FIG. 1, for example, illustrates some of the
advantages of horizontal directional drilling under a roadway 16.
The direction of the borehole 14 can be selectively changed, from
the downwardly directed portion 18 to the horizontally directed
portion 20 and then to the upwardly directed portion 22. Also
advantageous, but not limiting, is the ability to provide an entry
portion 24 and an exit portion 26 of the borehole 14 at the earth's
surface, thereby eliminating the need to excavate entry and exit
pits as is common with other methods of subterranean drilling.
Turning now to FIG. 2, which is an exploded isometric view of a
downhole portion of a drill string assembly 28. The drill string
assembly 28 is made up of a plurality of annular drilling members,
such as drill pipes 27, and a tool head 32 is attached to a distal
end of the drill string assembly 28. A bit 33 is attached to the
tool head 32. The drilling machine 10 (FIG. 1) acts on the drill
string 28 to rotate and/or thrust the bit 33 through the
subterranean earth.
An electronic transmitter 38 can be employed for use with an
above-ground receiver (not shown) to track the subterranean
location of the tool head 32 during drilling or backreaming
operations. Placing the transmitter 38 in the tool head 32 aids the
drilling machine 10 operator in steering the bit 33. It will be
noted the tool head 32 of FIG. 2 is partially broken away to reveal
a chamber 36 in the tool head 32 for receiving disposition of the
transmitter 38.
Heat build-up is a concern for both the transmitter 38 and the bit
33. Heat is generated by frictional forces created as the bit 33
engages the subterranean earth. A drilling fluid is commonly pumped
through the drill string 28 and the tool head 32 and sprayed onto
or near the bit 33 for cooling and lubricating the bit 33. While
flowing past the transmitter 38 and before being sprayed onto the
bit 33, the drilling fluid cools the transmitter 38.
A continuous fluid flow passage is thus necessary from the upper
end of the drill string 28 to the lower end of the tool head 32.
For example, the drill string 28 can have a longitudinal bore 40
fluidly connected with the chamber 36 in the tool head 32, wherein
the transmitter 38 is receivingly disposed. FIG. 3 illustrates the
tool head 32 can have a connecting portion, such as the threaded
tail piece 42, with a fluid passage 44 fluidly connecting the bore
40 of the drill string 28 with the chamber 36 of the tool head 32.
Another fluid passage 46 can extend from the opposing end of the
chamber 36 and terminate at a nozzle 48 aimed to spray the drilling
fluid onto or adjacent the bit 33.
Also disposed in the chamber 36 of the tool head 32 is a generator
assembly 52, which is more particularly detailed in the enlarged,
cross-sectional view of FIG. 4. The generator assembly 52 utilizes
the fluid flowing in the chamber 36 as a motive force to generate
power, as described below. Although the embodiment of FIG. 3
discloses the generator assembly 52 preferably contained, within
the tool head 32, the present invention is not thus limited,
whereas the generator assembly 52 could alternatively be positioned
elsewhere within the drill string 28, such as within the bore
40.
In FIG. 4 the drilling fluid flows under pressure in a direction
denoted by the reference arrow 54. The generator assembly 52 is
preferably adapted for a simple installation into the chamber 36.
For example, a stop 56 can depend from an inner surface 58 of the
tool head 32. A flange 60 of the generator assembly 52 can thereby
be readily positioned to engage the stop 56 so as to operably
position the generator assembly 52 within the chamber 36.
Conventional retention methods can be used to retain the generator
assembly 52 in the operable position.
As mentioned hereinabove and detailed below, the generator assembly
52 uses the drilling fluid as a motive force to generate power.
Typically, the generator assembly 52 is adapted to operate within a
preselected fluid flow range. Where the drilling fluid flow is
thereafter increased above the preselected range, it can be
advantageous to provide a bypass for a portion of the fluid flow to
substantially stabilize the effective fluid flow acting on the
generator assembly 52. That is, the bypass opens at pressures above
a preselected threshold pressure to substantially maintain a
selected flow at an inlet of the generator assembly 52, as shown
below.
One such manner is shown in FIG. 4, where one or more bypass valves
66 are normally closed and selectively openable to control the
amount of fluid flow passing therethrough as described hereinbelow.
The bypass valve 66 has a sealing member 68 that is biased in the
closed position by a spring 80 having a preselected stiffness so as
to be responsive to the desired fluid pressure in cracking open the
bypass valve 66.
The generator assembly 52 has a housing 70 defining a first cavity
72 and a second cavity 74. The first cavity 72 encloses a turbine
assembly 76 and the second cavity 74 encloses an electrical
generator 78. The housing 70 preferably forms a leading surface
projecting into the fluid flow to direct the fluid toward the
flange 60. For example, the housing 70 of FIG. 4 has a tapered
leading surface with a blunt nose portion 82 that is substantially
transverse to the fluid flow. A tapered transition portion 84
terminates at a rim portion 86 that is substantially parallel to
the fluid flow. A bulkhead 88 spans the rim portion 86 and
separates the first cavity 72 from the second cavity 74,
effectively isolating cavity 74 from the fluid. An inlet 90 and an
outlet 92 are provided in the housing 70, such as in the rim
portion 86 and the bulkhead 88, respectively.
The pressurized fluid thus flows through the inlet 90 into the
cavity 72 where it impingingly engages the turbine assembly 76.
Thereafter, an impulse-momentum transfer of energy occurs in
transferring fluid velocity to a mechanical rotation of a portion
of the turbine assembly 76. The fluid is afterward discharged from
the first cavity 72 through the outlet 92. Although for purposes of
the present description one inlet 90 is illustrated, it will be
understood that two or more inlets 90 can be provided in the
housing 70 as a matter of design choice. The selected number of
inlets 90 will depend, for example, on the fluid flow requirement
necessary to generate electrical energy for the desired signal
output or transmitter 38. The desired drilling speed, the type of
subterranean conditions, and the type of drilling tool utilized are
but a few of the numerous factors determining the fluid delivery
rate that must pass through drill string 28 to aid the drilling
process. In their combination inlets 90, outlets 92, and bypass
valves 66 must be sized to accommodate the maximum flow rate. Of
course, in one embodiment where no bypass valve 66 is used then the
size and configuration, that is the number and placement, of the
inlets 90 and outlets 92 determine the maximum flow rate. On the
other hand, the overall design parameters of generator assembly 52
in combination with the desired signal output of transmitter 38
define the minimum acceptable flow rate. As is known by those
skilled in the art, the various design parameters of this invention
must be adjusted to achieve an acceptable outcome without adversely
affecting drilling performance itself. Where two or more inlets 90
are utilized, preferably the inlets 90 would be circumferentially
arranged equidistantly in order to balance the loading effect of
the multiple fluid inlet streams against the turbine assembly 76.
Likewise, although only one outlet 92 is illustrated, two or more
outlets 92 can be provided in the housing 70 as a matter of design
choice.
The turbine assembly 76 generally has a rotatable impeller that is
rotated in response to the impinging engagement of the fluid. For
example, FIGS. 4 and 5 show the turbine assembly 76 having a
tangential impulse-momentum turbine, or turbine wheel 94 of the
Pelton wheel type. A supporting shaft 96 extends from the bulkhead
88 and supports a roller bearing 98. An inner race 100 of the
bearing 98 is affixed to the shaft 96 and an outer race 102 orbits
the inner race 100 upon a plurality of bearings 104, such as ball
bearings, needle bearings, or a hydrodynamic bearing interposed
therebetween.
The turbine wheel 94 has a hub 106 supported by the outer race 102
of the bearing 98, thereby supporting the turbine wheel 94 in
rotation around the shaft 96. The hub 106 has a first side 108
adjacent the bulkhead 88 and an opposing second side 110, and a
plurality of circumferentially arranged, radially extending vanes
112. At any particular rotational position of the turbine wheel 94,
one or more vanes 112 are impingingly engaged by the fluid flowing
through the inlet 90. FIG. 6 illustrates one particular rotational
position of the turbine wheel 94 whereat the fluid impingingly
engages a contact surface 114 of the vane 112, thereby imparting a
tangential impulse that, in turn, imparts momentum as a mechanical
rotation to the turbine wheel 94 in a direction denoted by the
arrow 116. It will be noted the inlet 90 is directed substantially
orthogonal to the axis of rotation of the turbine wheel 94 around
the shaft 96, and is located near the top of the rim portion 86 as
shown in FIG. 5 so as to impart a tangential force on the turbine
wheel 94.
Each of the vanes 112 is formed by an intersection of two radially
extending surfaces, the contact surface 114 and a relief surface
118. The contact surface 114 is impingingly engaged by the fluid,
but the relief surface 118 is preferably not so impingingly engaged
in order to urge the turbine wheel 94 only in the rotational
direction 116. FIG. 7 illustrates a subsequent position of the
turbine wheel 94, whereat the tip of the adjacent vane 112 first
enters the fluid stream flowing through the inlet 90. This view
best illustrates the angled relief surface 118 providing the
impinging engagement of the fluid against substantially only the
contact surfaces 114 of the adjacent vanes 112, so as to urge the
turbine wheel 94 only in the rotational direction 116. It will be
noted the contact surface 114 of FIGS. 5-7 provides a substantially
linear transition surface between adjacent relief surfaces 118.
Alternative configurations may be used as well, as is necessary for
characteristic fluid flow conditions and/or to meet predetermined
torque requirements of the turbine wheel 94, as is conventional
with the design and use of a Pelton-type wheel. FIGS. 7A and 7B,
for example, show an alternative turbine wheel 94A having vanes
112A. Vanes 112A have an arcuate contact surface 114A providing an
enhanced cupping surface for impinging engagement of the fluid
stream.
It has been determined that a generator assembly 52 employing no
bypass valves 66 and fitted with mechanical bearings can be
operated at as little as three gallons-per-minute flow rate and at
about 5000 RPM with a pressure drop of about 500 pounds per square
inch across the generator assembly 52. The maximum flow rate
without a bypass valve 66 is about 10 gallons-per-minute, but the
flow rate can be increased to more than two hundred
gallons-perminute with the addition of one or more bypass valves
66. These performance examples are illustrative of the spirit of
the present invention and are not intended to limit the spirit of
the invention in any way to the illustrative embodiments
described.
The present invention contemplates transferring this mechanical
rotation into power, such as by coupling the rotating turbine wheel
94 to a power generating device, such as the electrical generator
78. For example, returning to FIG. 4, it will be noted that the
first side 108 of the hub 106 of the turbine wheel 94 supports a
magnetically active member 120 in fixed rotation with the hub 106.
As will be seen below, the first magnetically active member 120 is
part of a coupling that links the turbine assembly 76 with the
electrical generator 78.
The electrical generator 78 in FIG. 4 is supported by the housing
70 within the second cavity 74. Generally, the electrical generator
78 is responsive to the mechanical rotation of the turbine assembly
76 to produce electrical power. For example, the electrical
generator 78 of FIG. 4 has a rotatable input shaft 122 that
supports a magnetically permeable member 124. The magnetically
active members 120, 124 are thus magnetically coupled across the
bulkhead 88. To provide this magnetic coupling the bulkhead 88
separating the magnetically active members 120, 124 comprises a
magnetically active material. The mechanical rotation of the
turbine wheel 94 imparts a mechanical rotation to the shaft 122 to
generate an electrical power output from the electrical generator
78. The magnetic coupling is preferred because such an arrangement
permits a completely sealed chamber 74 for receivingly disposing
the generator assembly 52.
Electrical leads 126 can be electrically connected and switched
accordingly to provide electrical power, as required, to other
components. For example, the generator assembly 52 of FIG. 4 can be
electrically connected to a rechargeable battery 128 which, in
turn, can be electrically connected by electrical leads 130 to
various electrical devices, such as the transmitter 38 (FIG. 3)
Alternatively, the electrical generator 78 can be electrically
connected directly to the transmitter 38 (FIG. 3). With an
appropriate selection of electrical generator 78 coupled to the
turbine assembly 76 as described hereinabove, it has been observed
that power ranging from two watts to 15 watts can be generated.
This is significantly greater than the power consumed by a
conventional battery powered transmitter 38, which is typically
about one watt.
FIG. 8 is a partial cross-sectional view of the tool head 32,
similar to that of FIG. 3 but illustrating an alternative
construction wherein the generator assembly 52a is reversed
relative to the fluid flow direction indicated by the reference
arrow 54. FIG. 9 is a detail cross sectional view of the generator
assembly 52a. The fluid flows into the inlet 90a and is expelled
from the cavity 72a through an opening 132 in the housing 70a.
Otherwise, the mechanical rotation of the turbine assembly 76 is
coupled to the electrical generator 78 substantially as described
above.
FIG. 10 is a generator assembly 52b built in accordance with
another alternative embodiment of the present invention. The
turbine assembly 76 is substantially similar to that previously
described. The electrical generator 78b, however, has one or more
electrical coils 134 positioned operably adjacent the magnetic
active member 120 of the turbine assembly 76. The rotation of the
magnetic active member 120 excites the coil 134 to produce a
current which is used to charge the rechargeable battery 128 or
power the transmitter 38 (FIG. 3) directly. In an alternative
embodiment the components of the electrical generator 78b can be
adapted for immersion in the fluid stream, so the portion of the
housing 70 enclosing the cavity 74 can be eliminated.
Returning to FIGS. 3 and 8 it will be noted that in a preferred
embodiment the generator assembly 52 is attached to the transmitter
38. The generator assembly 52 can be provided so as to replace the
end cap of a standard battery powered transmitter which would
otherwise retain the batteries within the battery compartment in
the transmitter. In a preferred embodiment this attachment to a
battery-powered transmitter would be provided by a threading
engagement of the generator assembly 52 and the transmitter 38. The
downhole generator of the present invention provides more
electrical power to the downhole end of a drill string than is
available in the current state of the art. Consequently, the
present invention enables the use of powered assemblies that are
not otherwise practicable in the drilling process. Downhole
detection systems such as ground-penetrating radar and gas
detectors illustrate devices with power requirements that are
greater than what can be practicably satisfied by existing downhole
power systems, but which can be readily satisfied by the
power-delivery capability of the present invention. It is
particularly advantageous to employ such detection systems
continuously while drilling. Additional power is also advantageous
in times when it is necessary to track the transmitter location
both during drilling and during backreaming.
The increased power provided by the present invention furthermore
makes possible the use of more sophisticated control systems to
enhance the overall drilling process, or selected elements thereof,
such as the steering action and/or navigation of tool head 32.
Power-hungry digital signal processing chips, for example, can be
employed for bi-directional transmission of data to and from the
transmitter. Complex integrated circuits can direct and apportion
electrical power that is sufficient to operate numerous fluid
actuators such as solenoid valves, pumps, switches and relays and
the like.
It is clear that the present invention is well adapted to attain
the ends and advantages mentioned as well as those inherent
therein. While a presently preferred embodiment of the invention
has been described for purposes of the disclosure, it will be
understood that numerous changes may be made which will readily
suggest themselves to those skilled in the art and which are
encompassed within the spirit of the invention disclosed and as
defined in the appended claims.
* * * * *